Systemic lupus erythematosus (SLE) is a chronic life threatening autoimmune disorder that afflicts well over one million Americans each year. It is characterized by the excessive production of a wide range of autoantibodies specific for self antigens such as chromatin, ribonucleoproteins and phospholipids. These antibodies and/or immune complexes containing these antibodies can deposit in blood vessel walls, glomeruli, and joints and contribute to complications ranging from glomerulonephritis to coagulation disorders. Studies conducted over the past funding cycle have demonstrated that the activation of autoreactive B cells is greatly enhanced by the ability of an autoantigen to effectively engage both the B cell receptor and either Toll-like receptor 9 (TLR9) or TLR7. It follows that the most prominent self-antigen targets in systemic autoimmune disease are essentially self-adjuvants. The purpose of this application is to further explore the factors that create and/or expose these self-adjuvants to the immune system. In particular, we will test the following hypotheses. (1) cell trauma and/or cell death may lead to modifications of host constituents that create novel endogenous TLR ligands;(2) endogenous TLR ligands serve as adjuvants for additional autoantigens with which they co-cluster;and (3) the autoantibody response is enhanced by type 1 IFN-induced upregulation of TLR7 expression in B cells. Specifically, we will: (1) determine whether DNA modifications, induced experimentally by treating DNA with agents that cause specific types of DNA damage or by exposing cells to UVA/UVB radiation, can increase the adjuvant activity of mammalian nucleic acid associated autoantigens, and evaluate the potential contribution of these self- adjuvants to the the development of SLE;(2) produce and characterize a panel of anti-phospholipid monoclonal antibodies that preferentially bind apoptotic cells at different stages of the apoptotic process and determine whether immune complexes consisting of membrane blebs bound by these antibodies can activate autoreactive B cells via a TLR-dependent mechanism;and (3) evaluate the direct effects of Type 1 IFN on the in vitro and in vivo proliferation, survival and function of autoreactive B cells Although current treatment regimens for SLE can reduce disease severity, they often have deleterious side effects that limit their extended use. A better understanding of the events that contribute to the initial activation of these autoreactive B cells will be critical to the development of more effective and less toxic therapies.